This invention relates to a harvester that is moved along the bottom of a body of water for the purpose of disloding and harvesting marine bivalve mollusks and other marine life from the bottom of the body of water, while avoiding adverse effects to the bottom such that continued replenishment of life at such locations does not become disrupted.
Historically, the collection or harvesting of marine bivalve mollusks, such as oysters, clams, and the like, has involved a hand operation in which an individual digs the bottom mud, silt or sand of the littoral zone with appropriate tongs, diggers or the like and dislodges the intertidal mollusks therefrom. Such procedure is labor intensive, tedious, costly, and subject to the personal whims of the individual harvesters.
In an attempt to improve upon the harvesting of bivalve mollusks and the like, prior attempts have been made to devise mechanical harvesters that move along the bottom of the littoral zone, normally when the tide is in and water covers the mollusk bed or colony, to dislodge the mollusks from the bottom mud, sand, bed or the like, and where appropriate, to segregate individual mollusks from cluster formations, after which the mollusks are collected and transported to an appropriate boat, barge, or other floating storage unit. Such prior attempts, while successful from the standpoint of removing the oysters, clams or the like from the beds of same, have been fraught with problems. Particularly, the prior attempts, as will be alluded to in more detail hereinafter, have been complicated and expensive devices, but most particularly in an attempt to remove the mollusk from the beds of same, the removal process has been accompanied by destruction of the strata in which the mollusks live. For example, a hydraulic clam dredge was referred to by Aristotle around 344 B.C. and his treatise, History of Animals, wherein he states: "In the Pyrrhaean Strait, the clam was exterminated, partly by the dredging machine used in their capture . . . ". Yet, much more recently, hydraulic clam dredges have been utilized extensively for harvesting clams, which dredges operate on the principle of mechanically slicing a horizontal layer of bottom sediment, after which the solids in the layer are dispersed and dislodged with high pressure jets of water. Clams and oysters along with rather large quantities of additional foreign matter are then elevated to the surface to be loaded onto a boat, barge, or other receptacle. Obviously, since a significant portion of the bottom sediment is removed, large power requirements are required to generate force adequate to push the dredge through the sediment, and also to lift same, while likewise the energy required for high volume, high pressure pumping of fluid for washing the clams is extremely high.
A semi-hydraulic dredge is set forth in U.S. Pat. No. 2,508,087 which dislodges oysters from an oyster bed by relatively gentle flow of water and deposits the dislodged oysters on a screen conveyor, which transports the oysters to the surface while permitting sand, gravel, silt and the like to pass through the screen and return to the water. A further mechanical harvester for intertidal cluster oysters has been developed which includes a rotating digging element which digs into the bottom, removing virtually everything therefrom. Water is then pumped against the load to remove silt, etc. and force the oysters into a chute and onto a vessel.
Still another harvester head has been developed that includes a rectangular steel box in which two steel cylinders are affixed with flexible steel tines. The cylinders, powered by a hydraulic motor, rotate in the direction of travel, raking oysters and clams from the bottom which are conveyed to the surface by an escalator device.
Most pertinent perhaps is a predecessor project to the present invention which is defined along with the aforementioned prior harvester attempts in a paper by Andrew G. Jordan et al, entitled "Development of Equipment for the Mechanical Harvest of Oysters in South Carolina: Progress Report", presented at the 1975 annual meeting of the American Society for Agricultural Engineers in Davis, Calif., June 22-25, 1975. The Jordan et al mechanical harvester includes a sled associated with a boat for movement along an oyster bed. The sled includes a harvester head employing a first, tined loop element that is rotatable in the direction of movement of the sled to dislodge oysters from an oyster bed, and a second tined loop element located behind the dislodgement element, rotatable in an opposite direction to pick up dislodged oysters and convey same to an escalator, a front end of which was associated with the sled and a rear end of which, with the boat. While the Jordan et al mechanical harvester was successful in harvesting intertidal oysters, the significant overall weight of the sled and escalator did create problems. Particularly the oyster bed supporting strata was damaged which as discussed hereinafter, is quite undesirable.
Oyster spat, sperm of the oyster, is found in the water during particular times of the year, generally May or June. The spat are mobile in the water until they succeed in finding an appropriate point for securement. Once the spat becomes affixed, it is thereafter immobile, and grows into an oyster, which likewise includes the production of the oyster shell. Attachment of the spat occurs on a firm support, such as pilings, rocks and the like, though predominantly on previously existing oyster beds where the firm support surface is a firm strata which may include dead or live oyster shells. As the oyster population increases in an oyster bed, oyster clusters are formed which, unless properly harvested, become overly dense to a point where the bottom layers of oysters in the cluster may become eventually covered with silt and die. An unharvested bed would thus continue to build until there is no available room, even at high tide, for additional spat to attach, whereupon the oyster bed will eventually die out and remain in place. Such of course reduces the productive capacity of oysters along the coast line, and creates impediments to boating, and the like. On the other hand, when an oyster bed is properly harvested, without damage to the underlying strata, new spat will attach to the remaining strata during the spawning season and the bed will continue to produce for future harvesting. While, as mentioned above, prior art harvesters were successful in harvesting the oysters, certainly more effectively than by hand, all of the known prior art harvesters generally destroyed or at least impaired the firm strata of the bed, whereby replenishment of the bed to a harvestable condition has required a number of years, if ever.
The mechanical harvester of the present invention overcomes the aforementioned problems of the prior art mechanical harvesters, in that, oysters, clams and the like may be effectively, and economically harvested without the danger of damaging the underlying firm strata. Consequently, the same oyster bed will remain productive and is again ready for harvesting, generally in two years. Additionally, and quite importantly, the mechanical harvester of the present invention is capable of effectively and economically removing oysters from one area and redepositing same at a more desirable location for proper oyster growth. For example, as has been publicized greatly in the last few years, mollusks such as clams and oysters, have often been located in polluted environs, whereby human consumption of same is precluded. By utilization of the mechanical harvester of the present invention, however, these polluted mollusks may be removed from the contaminated environs and transported to a clean, and acceptable environment. Once located in the clean environment, the mollusk will purge itself of the pollution contaminants in the matter of a few weeks, and thereafter will be available for harvesting and human consumption. This procedure thus improves the managerial possibilities for aquaculture.
Still further, commercial oystering operations are generally required by law to reseed oyster bed areas with old shells which assists in reestablishment of the harvested oyster beds. Such can be accomplished by the harvester of the present invention.
The mechanical harvester of the present invention is far more efficient than the prior mechanical harvesters, is capable of operation in varying water levels, and effectively harvests mollusks in a fashion heretofore unseen. The prior mechanical harvesters described above are deficient in teaching or suggesting the mechanical harvester according to the present invention.